The present invention relates generally to a charging generator control apparatus for a vehicle, and more particularly to a control apparatus for a vehicle battery charging generator adapted to control field current flowing through a field coil of the charging generator, thereby regulating the output voltage to be supplied to the battery and an electric load.
To facilitate the understanding of the present invention, reference is made to FIG 1 which is a circuit diagram, disclosed in Japanese Patent Laid-Open Application No. 59-9949/1984, showing a typical example of a conventional control apparatus for a charging generator for use in a vehicle. Referring to FIG. 1, there is shown an alternating current generator 1, having armature coils 101 and a field coil 102 and driven by an engine (not shown) to produce a three-phase AC voltage. There is also shown a rectifier 2 which carries out the full-wave rectification for the three-phase AC voltage from the generator 1, and provides a rectified output current at its output terminals 201, 202 and 203. It is seen that the field current flowing through the field coil 102 of the generator 1 is controlled by way of a voltage regulator 3 in such a manner that after the generator 1 has started, the output voltage of the generator 1 may be controlled to a predetermined level by the voltage regulator 3.
The voltage regulator 3 includes a diode 301 for absorbing a surge voltage and a power transistor 302 connected in series to the diode 301 and ground. The field coil 102 is connected to the output terminal 202 of the rectifier 2 and across the diode 301. The power transistor 302 is employed in the circuit of the voltage regulator 3 to repeatedly interrupt the flow of field current in the coil 102 and includes a base connected to the collector of the transistor 304 and also to the output terminal 202 through a base resistor 303. The emitter of the transistor 304 is grounded together with the emitter of the power transistor 302, and the base of the transistor 304 is connected to a common node A of resistors 306 and 307 through a zener diode 305. The transistor 304 is adapted in the circuit to repeatedly interrupt the current flowing through the power transistor 302, and the zener diode 305 is adapted to detect the output voltage of the rectifier 2, and is turned on when this output voltage exceeds a predetermined value.
There is also shown a series circuit consisting of resistors 306-308 between the output terminal 202 and ground. These resistors 306-308 form a voltage divider to divide the output voltage at the output terminal 202 of the rectifier 2.
A determining voltage regulating circuit 4 includes a transistor 401 having its collector and emitter connected in parallel with the resistor 308 of the voltage regulator and a series combination of resistors 402 and 403 connected to a movable contact of a key switch 6.
The node B between the resistors 402 and 403 is connected through an acceleration switch 8 and a light switch 10 to the positive electrode of a storage battery 7. The negative electrode of the battery 7 is grounded.
The acceleration switch 8 comprises a switch which is connected to, for example, an appropriate pressure responsive means (not shown). The node C between the acceleration switch 8 and the light switch 10 is grounded through a lighting device 9. This lighting device 9 can be lit by closing the light switch 10. The positive electrode of the battery 7 is also connected to the output terminal 201 of the rectifier 2, and to the output terminal 202 through the key switch 6 and a resistor 5.
In operation, when the key switch 6 is closed, a field current for the field coil 102 is produced from the battery 7 and flows through the key switch 6, resistor 5, the field coil 102 and the power transistor 302. This initial field current excites the armature coils 101 and prepares the generator 1 for its power generating operation.
At the same time, the voltage of the battery 7 is also applied to the determining voltage regulating circuit 4 through the key switch 6. With this operation, the transistor 401 is now made conductive, thus short-circuiting the resistor 308.
Under this normal (steady) state of operation of the circuit, a current potential at node A as a voltage detection point of the voltage regulator 3 may be determined from the divided voltage in the voltage divider circuit consisting of resistors 306 and 307.
Next, when the engine of a vehicle (not shown) starts and the generator 1 is driven, the generator 1 generates electric power, and the voltage regulator 3 operates to control the output voltage of the generator 1 to a predetermined regulated voltage. Therefore, the generator 1 supplies the battery 7 and other electric loads (not shown) with the thus-regulated output voltage.
With such an arrangement of the control apparatus for the vehicle battery charging generator as noted above, when the acceleration switch 8 is closed as the vehicle is accelerated, the node B of the determining voltage regulating circuit 4 is then grounded by way of the acceleration switch 8 and the filament of the lighting device 9 and so is dropped in potential.
As a consequence, the transistor 401 is then switched off, and the resistor 308 is released from its short-circuit state. Then, a voltage divider circuit consisting of the resistor 306 and the resistors 307 and 308 is formed for the voltage detection by the voltage regulator 3, thus increasing the potential at the node A.
Under this condition, the zener diode 305 and the transistor 304 become conductive while the power transistor 302 is not conductive, so that the field ccurrent is interrupted and thus the generator 1 stops its power generation. This serves to remove the driving torque of the generator 1 from the engine's load, thereby enhancing the acceleration performance of the vehicle.
Next, when the acceleration operation is absent and the acceleration switch 8 is opened, the potential at the node B of the determining voltage regulating circuit 4 will increase and the transistor 401 will again become conductive, thus short-circuiting the resistor 308. Therefore, the voltage regulator 3 again returns again to the normal state of operation of the vehicle as stated above.
Now, referring to a state in which the lighting device 9 is operating, i.e., the light switch 10 is closed so that the potential at the node C is equal to the voltage of the battery 7, when the vehicle is accelerated and the acceleration switch 8 is closed, the node B of the determining voltage regulating circuit 4 becomes equal in potential to the node C, thus being applied with the battery voltage. Under such a condition, since the transistor 401 maintains its conductive state to short-circuit the resistor 308, the voltage regulator 3 continues its normal operation, thus causing the generator 1 to be in the power generation operation mode of operation without any interruption.
In this manner, even when the vehicle is accelerating while the lighting device 9 is lit, there is no interruption of the power generating operation on the part of the generator 1, which thus prevents the lighting device 9 from changing quickly in its intensity of illumination.
With this construction of the control apparatus for the conventional charging generator for use in a vehicle, while the lighting device 9 is lit, the driving torque of the generator 1 is continuously imposed as a load on the vehicle's engine because the generator 1 does not cease its power generating operation even during the acceleration mode of the vehicle in order to prevent the intensity of illumination of the lighting device 9 from rapidly changing. Furthermore, while the lighting device 9 is not lit in the acceleration mode, since the generator 1 rapidly and repeatedly stops and starts the power generation, the driving torque of the generator 1 which forms a load on the engine is rapidly changed causing an even engine rotation
On the other hand, Japanese Patent Application Laid-open No. 59-99939 discloses a vehicle battery charging generator control apparatus in which the power generation of the generator is stopped during the acceleration time of the vehicle but is not stopped while a lighting device is on.